JP7172024B2 - Chalcogenide glass material - Google Patents

Description

The present invention relates to a chalcogenide glass material used for infrared sensors, infrared cameras and the like.

In-vehicle night vision systems, security systems, and the like are equipped with infrared sensors used for biometric detection at night. Since the infrared sensor senses infrared rays with a wavelength of about 8 to 14 μm emitted from a living body, an optical element such as a filter or lens that transmits infrared rays in this wavelength range is provided in front of the sensor section.

Ge and ZnSe are mentioned as a material for the above optical elements. Since these materials are crystalline, they are inferior in workability and difficult to process into complicated shapes such as aspherical lenses. Therefore, there is a problem that mass production is difficult and it is also difficult to miniaturize the infrared sensor.

Therefore, chalcogenide glass has been proposed as a vitreous material that transmits infrared rays with a wavelength of about 8 to 14 μm and is relatively easy to process. (See Patent Document 1, for example)

JP 2009-161374 A

However, the glass described in Patent Literature 1 has a significantly reduced infrared transmittance at a wavelength of 10 μm or longer, and is particularly poor in sensitivity to infrared rays emitted from a living body, and the infrared sensor may not function satisfactorily. Furthermore, the glass has a problem that it deteriorates due to its low weather resistance, and the infrared transmittance decreases.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a chalcogenide glass material that has excellent weather resistance and is suitable as an optical element for an infrared sensor.

The chalcogenide glass material of the present invention is characterized by containing 20 to 99% by mol of Te and having an antireflection film formed on the surface thereof.

Since the chalcogenide glass material of the present invention contains Te as an essential component, it is excellent in infrared transmittance. In addition, since an antireflection film is formed on the surface, reflection of infrared light can be suppressed, and infrared transmittance can be further increased. Furthermore, when an antireflection film is formed on the surface, the glass can be prevented from reacting with moisture and oxygen in the air and deteriorating, so that the glass has excellent weather resistance.

The chalcogenide glass material of the present invention preferably contains 40 to 95% by mole of Te.

The chalcogenide glass material of the present invention preferably further contains 0 to 40% by mole of Ge.

The chalcogenide glass material of the present invention preferably further contains 0 to 30% Ga in terms of mol %.

In the chalcogenide glass material of the present invention, the antireflection film preferably has a total of two or more layers of alternating low refractive index layers and high refractive index layers.

An optical element of the present invention is characterized by using the chalcogenide glass material described above.

An infrared sensor of the present invention is characterized by using the optical element described above.

According to the present invention, it is possible to provide a chalcogenide glass material that is excellent in weather resistance and suitable as an optical element for an infrared sensor.

The chalcogenide glass material of the present invention has an antireflection film formed on its surface. As described above, when an antireflection film is formed on the surface, infrared transmittance and weather resistance can be improved.

First, the antireflection film will be explained.

It is preferable that the antireflection film has a total of 2 or more layers, 2 to 34 layers, particularly 4 to 12 layers, in which low refractive index layers and high refractive index layers are alternately laminated. If the number of laminations is too small, it becomes difficult to transmit infrared light. On the other hand, if the number of laminations is too large, the number of steps required for film formation increases, which tends to cause an increase in cost. The combination of the low refractive index layer and the high refractive index layer is not limited as long as the refractive index of the high refractive index layer is relatively higher than that of the low refractive index layer.

The thickness of each refractive index layer is preferably 0.01 to 10 μm, 0.02 to 5 μm, particularly 0.03 to 2 μm. If the thickness per layer is too small, it becomes difficult to transmit infrared light. On the other hand, if the thickness is too large, the stress applied to the interface between the antireflection film and the chalcogenide glass material increases, and the adhesion of the film and the mechanical strength of the glass material tend to decrease.

The material of the refractive index layer is metal oxide _{( Y2O3 , Al2O3 ,} SiO, _SiO2 , MgO, TiO, _TiO2 , _Ti2O3 , _CeO2 , _{Bi2O3 , HfO2} ), Hydrogenated carbon, diamond-like carbon (DLC), Ge, Si, ZnS, ZnSe, _As2S3 , _{As2Se3 , PbF2} , metal telluride, and metal fluoride _are preferred. In order to further improve weather resistance and mechanical strength, it is preferable to use metal oxide, hydrogenated carbon, or diamond-like carbon (DLC) as the outermost layer. Moreover, in order to further improve adhesion, it is preferable to use a metal oxide as the intermediate layer. The material of the refractive index layer may be a resin, for example, an olefin resin or the like.

Next, the composition of the chalcogenide glass material of the present invention will be described. In the following description of the content of each component, "%" means "mol %" unless otherwise specified.

The chalcogenide glass material of the present invention contains Te as an essential component. Te, which is a chalcogen element, is a component that forms a glass skeleton and increases infrared transmittance. The Te content is 20 to 99%, preferably 40 to 95%, 50 to 85%, 60 to 85%, particularly 70 to 80%. If the Te content is too low, vitrification becomes difficult and the infrared transmittance tends to decrease. On the other hand, if the Te content is too high, the thermal stability of the glass tends to decrease, and Te-based crystals tend to precipitate. Incidentally, the other chalcogen elements Se and S are more difficult to improve the infrared transmittance than Te, and tend to have a shorter infrared transmission limit wavelength.

In addition to the above components, various components shown below can be contained.

Ge is a component that widens the vitrification range and increases the thermal stability of the glass without lowering the infrared transmittance. The Ge content is preferably 0-40%, 1-35%, 5-30%, 7-25%, particularly 10-20%. If the Ge content is too high, Ge-based crystals tend to precipitate more easily and raw material costs tend to increase.

Ga is a component that widens the vitrification range and increases the thermal stability of the glass without lowering the infrared transmittance. The Ga content is preferably 0 to 30%, 1 to 30%, 3 to 25%, 4 to 20%, particularly 5 to 15%. If the Ga content is too high, Ga-based crystals tend to precipitate more easily and raw material costs tend to increase.

Ag is a component that widens the vitrification range and enhances the thermal stability of the glass. The Ag content is preferably 0 to 20%, particularly 1 to 10%. If the Ag content is too high, it becomes difficult to vitrify.

Al is a component that widens the vitrification range and enhances the thermal stability of the glass. The Al content is preferably 0 to 20%, particularly 0 to 10%. If the Al content is too high, it becomes difficult to vitrify.

Sn is a component that widens the vitrification range and enhances the thermal stability of the glass. The Sn content is preferably 0 to 20%, particularly 0 to 10%. If the Sn content is too high, it becomes difficult to vitrify.

Next, the method for producing the chalcogenide glass material of the present invention will be described.

Raw materials are mixed to obtain the above glass composition to obtain a raw material batch. Next, after the quartz glass ampoule is evacuated while being heated, a raw material batch is put therein, and the quartz glass ampoule is sealed with an oxygen burner while being evacuated.

As raw materials, element raw materials (Te, Ge, Ga, etc.) may be used, and compound raw materials (GeTe, GeTe ₂ , Ga ₂ Te ₃ , etc.) may be used. Moreover, it is also possible to use these together.

Next, the sealed quartz glass ampoule is heated to 650 to 1000° C. at a rate of 10 to 80° C./hour in a melting furnace and held for 6 to 12 hours. During the holding time, the quartz glass ampoule is turned upside down to stir the melt, if necessary.

Thereafter, the quartz glass ampoule is taken out from the melting furnace and rapidly cooled to room temperature to obtain a glass preform.

Subsequently, the obtained glass base material is processed into a predetermined shape (disk-like, lens-like, etc.).

A chalcogenide glass material is obtained by forming an antireflection film on one or both sides of a glass base material processed into a predetermined shape. Methods for forming the antireflection film include a vacuum deposition method, an ion plating method, a sputtering method, and the like.

After forming the antireflection film on the glass base material, the glass base material may be processed into a predetermined shape. However, since the antireflection film tends to peel off during the processing step, it is preferable to form the antireflection film after processing the glass base material into a predetermined shape unless there are special circumstances.

The chalcogenide glass material of the present invention preferably has an average infrared transmittance of 80% or more, 85% or more, particularly 90% or more at a wavelength of 8 to 14 μm with a thickness of 2 mm. If the average infrared transmittance is too low, it may not function sufficiently when used as an infrared sensor.

Since the chalcogenide glass material of the present invention is excellent in infrared transmittance and weather resistance, it can be used as an optical element such as a cover member for protecting the sensor part of an infrared sensor or a lens for concentrating infrared light on the infrared sensor part. It is suitable as

EXAMPLES The present invention will be described below based on examples, but the present invention is not limited to these examples.

Tables 1 and 2 show examples of the present invention (samples Nos. 1 to 10) and comparative examples (samples Nos. 11 and 12).

Raw materials were blended so that the glass compositions shown in Tables 1 and 2 were obtained, and raw material batches were obtained. Next, after the quartz glass ampoule washed with pure water was heated and evacuated, a raw material batch was put therein, and the quartz glass ampoule was sealed with an oxygen burner while being evacuated. The sealed quartz glass ampoule was heated to 650 to 1000° C. at a rate of 10 to 80° C./hour in a melting furnace and held for 6 to 12 hours. During the holding time, the quartz glass ampoule was turned upside down every 2 hours to stir the melt. Thereafter, the quartz glass ampoule was taken out from the melting furnace and rapidly cooled to room temperature to obtain a glass preform.

The obtained glass base material was cut and polished to be processed into a disk shape having a diameter of 15 mm and a thickness of 2 mm, and both surfaces were optically polished. An anti-reflection film having the structure shown in Tables 1 and 2 was formed on the entire surface of the optically polished glass base material by vacuum deposition to obtain a chalcogenide glass material. Regarding the antireflection film, as shown in Tables 1 and 2, from the glass material side, the first layer, the second layer, the third layer, the fourth layer, the fifth layer, the sixth layer, the seventh layer, and the third layer. The 8th layer, the 9th layer, the 10th layer, the 11th layer, the 12th layer, and the 13th layer were formed in this order.

The obtained samples were measured or evaluated for average infrared transmittance and weather resistance. Tables 1 and 2 show the results.

The average infrared transmittance at a wavelength of 8 to 14 μm was measured by FT-IR (Fourier transform infrared spectrophotometer).

Weather resistance was evaluated as follows. The obtained sample was kept in a constant temperature and humidity layer of 60° C.-90 Rh % for 500 hours. After holding, the average infrared transmittance at a wavelength of 8 to 14 μm was measured by FT-IR. When the average infrared transmittance did not change before and after holding, it was evaluated as "○", and when it changed, it was evaluated as "X".

As is clear from Tables 1 and 2, the samples of Examples 1 to 10 had a high average infrared transmittance of 94% or more and excellent weather resistance. On the other hand, in Comparative Example 1, since no antireflection film was formed, the average infrared transmittance was as low as 52%, and the weather resistance was also poor. Comparative Example 2 did not contain Te, so the average infrared transmittance was as low as 68%.

INDUSTRIAL APPLICABILITY The chalcogenide glass material of the present invention is suitable as a cover member for protecting the sensor portion of an infrared sensor and as an optical element such as a lens for concentrating infrared light on the infrared sensor portion.

Claims (9)

A chalcogenide glass material containing 20 to 99% by mol of Te and having an antireflection film formed on its surface,
The antireflection film is formed by laminating a total of two or more layers of a low refractive index layer and a high refractive index layer alternately,
_The outermost layer of the antireflection film is a metal oxide selected from Y2O3 , Al2O3 _{, MgO} , _{CeO2 ,} Bi2O3 , HfO2 _{, hydrogenated} carbon _or ZnS . is either
The _first layer of the antireflection film on the glass material _side is any metal oxide selected from Ge, Si , Y2O3 , _{Al2O3 ,} MgO, CeO2 _, and HfO2 _. A chalcogenide glass material comprising: 2. The chalcogenide glass material according to claim 1, characterized by containing 40 to 95% Te in terms of mol %. 3. The chalcogenide glass material according to claim 1, further comprising 0 to 40 mol % of Ge. 4. The chalcogenide glass material according to claim 1, further comprising 0 to 30% Ga in terms of mol %. 5. The chalcogenide glass material according to claim 1, wherein the thickness of each refractive index layer is 0.01 to 2 μm. 6. The chalcogenide glass material according to claim 1, wherein the outermost layer of said antireflection film is ZnS. A chalcogenide glass material containing 20 to 99% by mol of Te and having an antireflection film formed on its surface,
The antireflection film is formed by laminating a total of two or more layers of a low refractive index layer and a high refractive index layer alternately,
The outermost layer of the antireflection film is ZnS,
The first layer of the antireflection film on the glass material side contains Ge, Si, Y ₂ O. ₃ , Al ₂ O. ₃ , MgO, CeO ₂ , HfO ₂ A chalcogenide glass material characterized by being any metal oxide selected from any one of An optical element comprising the chalcogenide glass material according to any one of claims 1 to 7 . An infrared sensor using the optical element according to claim 8 .